1. Field of the Invention
This invention relates to a magnetic disk cartridge provided with a magnetic disk, a shell for housing the magnetic disk therein, and a shutter for opening and closing a hole formed in the shell for insertion of a magnetic head. This invention particularly relates to a hole provided for insertion of a shutter spring for urging the shutter to the position that closes the hole for insertion of a magnetic head.
2. Description of the Prior Art
There have heretofore been known magnetic disk cartridges provided with a magnetic disk, a shell for housing the magnetic disk therein, and a shutter having a U-shaped cross section and slideably fitted to the shell for opening and closing a hole formed in the shell for insertion of a magnetic head.
FIG. 4 is a bottom view showing an example of the conventional magnetic disk cartridge. With reference to FIG. 4, a conventional magnetic disk cartridge 1 comprises a thin box-like shell 2 composed of an upper shell half 2a and a lower shell half 2b which have approximately symmetrical shapes and are joined together. A magnetic disk 4 provided with a metal center core 3 at the center is housed in the shell 2, and the center core 3 is exposed to the exterior via a circular center hole 2c formed in the shell 2. In the course of recording and reproduction of information, the magnetic disk cartridge 1 is fed into a magnetic disk drive device for recording and reproduction, the center core 3 is magnetically chucked to a spindle in the drive device, and the magnetic disk 4 is rotated in the shell 2 by the spindle.
Recording of the information on the magnetic disk 4 or reproduction of information therefrom is carried out by the contact of the magnetic head, which is provided in the drive device, with the rotating magnetic disk 4. Therefore, a rectangular hole 5b for insertion of the magnetic head into the lower shell half 2b is formed in the lower shell half 2b in the radial direction of the magnetic disk 4, and a hole 5a for insertion of the magnetic head or a pad into the upper shell half 2a is formed in the same shape as the shape of the hole 5b at the position of the upper shell half 2a that corresponds to the position of the hole 5b.
The hole 5a for insertion of the magnetic head or the pad and the hole 5b for insertion of the magnetic head (both will hereinafter be simply referred to as the hole 5 provided for insertion of the magnetic head) are closed for prevention of dust entry and protection of the magnetic disk 4 as long s the magnetic head is not to be inserted into the hole 5 provided for insertion of the magnetic head. Only in the course of recording and reproduction, the hole 5 provided for insertion of the magnetic head is opened to expose the magnetic disk 4 to the exterior. FIG. 5 is a bottom view showing the shutter in FIG. 4, and FIG. 6 is a sectional view taken along line VI-VI of FIG. 5. Specifically, the hole 5 provided for insertion of the magnetic head is covered by a shutter 6 as shown in FIGS. 5 and 6. The shutter 6 is composed of an upper plate 7, a lower plate 8, and a connection plate 9 for connecting the upper plate 7 and the lower plate 8 with each other. The lower plate 8 is provided with an opening 10 having a shape nearly equal to or slightly larger than the shape of the hole 5 provided for insertion of the magnetic head. Also, The upper plate 7 is provided with a opening 11 similar to the opening 10 at the position corresponding to the opening 10. The shutter 6 is fitted to the shell 2 over a front edge face 2d thereof so that the shutter 6 is slideable between a hole closing position at which the upper plate 7 and the lower plate 8 close the hole 5 provided for insertion of the magnetic head as shown in FIG. 4 and a hole opening position at which the openings 10 and 11 align with the hole 5 provided for insertion of the magnetic head as shown in FIG. 7. Also, the shutter 6 is urged by a shutter spring 12 toward the hole closing position in the direction as indicated by the arrow A. In general, a torsion coil spring is used as the shutter spring 12. FIG. 8 is a bottom view showing the shutter spring 12 shown in FIG. 4, and FIG. 9 is a front view showing the shutter spring 12 shown in FIG. 4. The shutter spring 12 is made by coiling a stainless steel wire several turns. A left arm 14 and a right arm 15 extend linearly from both ends of a coiled portion 13. A bent portion 14a is formed downward at the extremity of the left arm 14 at an angle approximately normal to the left arm 14, and a bent portion 15a is formed upward at the extremity of the right arm 15 at an angle approximately normal to the right arm 15 (the upward-downward direction coincides with the height direction of the coiled portion 13). Also, the lengths of the left arm 14 and the right arm 15 are equal to each other, and the lengths of the bent portion 14a and the bent portion 15a are equal to each other. Thus the left arm 14 and the bent portion 14a are symmetrical with the right arm 15 and the bent portion 15a with respect to a point.
As shown in FIG. 4, the shutter spring 12 is provided at the rear position as viewed in the urging direction for the shutter 6 as indicated by the arrow A, and urges the shutter 6 to the position that closes the hole 5 provided for insertion of the magnetic head by the resilient urging force of the arms 14 and 15. Also, at the time the hole 5 provided for insertion of the magnetic head is to be opened, the shutter 6 is moved to the hole opening position as shown in FIG. 7 against the resilient urging force of the arms 14 and 15.
FIG. 10 is a front view showing the major part of the magnetic disk cartridge as viewed from the direction as indicated by the arrow X in FIG. 4, FIG. 11 is a bottom view showing the major part of the magnetic disk cartridge as viewed from the direction as indicated by the arrow XI in FIG. 10, FIG. 12 is a sectional view taken along line XII--XII of FIG. 11, and FIG. 13 is a sectional view taken along line XIII-XIII of FIG. 11. The shutter spring 12 is provided in the condition as shown in FIGS. 10, 11, 12 and 13.
Specifically, the bent portion 15a of the right arm 15 of the shutter spring 12 is inserted into and held in a recess 16 formed on the inner side of the upper shell half 2a. The bent portion 14a of the left arm 14 is engaged with a hook-like engagement portion 9a formed by bending a part of the connection plate 9 of the shutter 6 inwardly. As shown in FIG. 12, the recess 16 is surrounded by a front wall 2a' of the upper shell half 2a, a front wall 2b' of the lower shell half 2b, and an overhang 18 formed on the upper shell half 2a. Therefore, the bent portion 15a inserted into the recess 16 does not fall in the vertical and horizontal directions in FIG. 12, and is secured in the recess 16 by being pushed by the resilience of the shutter spring 12 itself against the edge face of the recess 16 on the side opposite to the shutter 6.
The bent portion 14a of the left arm 14 is engaged with the hook-like engagement portion 9a, and is prevented from disengagement from the engagement portion 9a by the combination of the engagement portion 9a, the connection plate 9 of the shutter 6, with the upper shell half 2a.
FIG. 14 is a schematic view showing the method of fitting the shutter spring 12 into the shell 2. With reference to FIG. 14, in the course of the manufacturing process, the shutter spring 12 is fitted into the shell 2 by bending the left arm 14 and the right arm 15 so that the shutter spring 12 can be inserted into a hole 17 which is provided for insertion of the shutter spring and which is opened at the front edge face 2d of the shell 2 at the time the shutter 6 is present at the hole closing position as shown in FIG. 14, and inserting the coiled portion 13 and then the arms 14 and 15 into the predetermined position inside of the shell 2 by use of a pusher 19. Such a method of fitting the shutter spring 12 into the shell 2 by use of an automatic machine is preferable from the viewpoint of simplification of the manufacturing process. As shown in FIGS. 10 and 11, in order to facilitate the fitting of the shutter spring 12, a step-like portion 21a provided with a rearward front edge face 21 positioned rearward from a main front edge face 20 of the upper shell half 2a as viewed in the direction as indicated by the arrow D in FIG. 11 is formed at the front edge region of the upper shell half 2a at the position corresponding to the hole 17 provided for insertion of the shutter spring 12. The step-like portion 21a continues to the aforesaid overhang 18. Also, a step-like portion 24a provided with a rearward front edge face 24 positioned rearward from a main front edge face 23 which is positioned at the same forward position as the main front edge face 20 of the upper shell half 2a is formed at the front edge region of the lower shell half 2b at the position corresponding to the hole 17 provided for insertion of the shutter spring 12.
In the case where the shutter spring 12 is inserted into the shell 2 by the method as mentioned above, the bent portion 15a of the right arm 15 is guided by the step-like portion 21a and the overhang 18, and is reliably held in the recess 16. However, as shown in FIG. 15, at the time the shutter spring 12 is inserted into the shell 2, there is the risk of the shutter spring 12 being deviated toward the lower plate 8 of the shutter 6, so that the extremity of the bent portion 14a of the left arm 14 interferes with the right edge face of the lower plate 8 and insertion of the bent portion 14a into the predetermined position becomes impossible. Therefore, special devices and accurate adjustments with respect to molds for the upper shell half 2a and the lower shell half 2b have heretofore been required in the procedure for fitting the shutter spring 12 by use of the automatic machine. To eliminate this problem, it may be considered to, for example, divide the process of insertion of the shutter spring 12 into two steps, insert a part of the shutter spring 12 or the extremity of the bent portion in the first step, and insert the remainder in the second step. However, this method has various problems such that the manufacturing process becomes complicated, and the equipment cost becomes high.